Use gray-matter fork with updated js-yaml dependency

jonschlinkert/gray-matter#137 (comment)

Author: MattiasBuelens

package-lock.json

@@ -62,6 +62,9 @@
     "unist-util-visit": "^5.0.0"
   },
   "overrides": {
+    "@docusaurus/utils": {
+      "gray-matter": "npm:@gr2m/gray-matter@4.0.3-with-pr-137"
+    },
     "docusaurus-theme-openapi-docs": {
       "react": "$react"
     }